Measurement of Run Out and Concentricity

Introduction

The measurement of run out and concentricity plays a crucial role in metrology and mechanical measurements. These measurements help ensure the proper alignment and balance of rotating parts, identify and correct manufacturing defects, and improve the overall performance and reliability of mechanical systems.

In this article, we will explore the fundamentals of run out and concentricity measurements, different measurement techniques, real-world applications, and the advantages and disadvantages of these measurements.

Measurement of Run Out

Run out refers to the deviation of an object's rotating axis from its true geometric center. It can occur in two ways: radial run out and axial run out.

Radial Run Out

Radial run out refers to the variation in the distance between the rotating axis and a reference point on the object's surface. It is measured perpendicular to the axis of rotation.

Axial Run Out

Axial run out, on the other hand, refers to the variation in the distance between the rotating axis and a reference plane. It is measured parallel to the axis of rotation.

To measure run out, various techniques can be used, such as the dial indicator method and laser measurement method.

The dial indicator method involves using a dial indicator to measure the deviation of the rotating object's surface from a reference point. The indicator is placed in contact with the surface, and the readings are taken at multiple points around the circumference.

The laser measurement method utilizes laser technology to measure the run out of an object. A laser beam is directed towards the rotating object, and the reflected beam is analyzed to determine the run out.

To understand the measurement process better, let's walk through a typical run out measurement problem and its solution:

1. Set up the dial indicator or laser measurement equipment.
2. Position the indicator or laser beam on the rotating object's surface.
3. Rotate the object and record the readings at multiple points.
4. Calculate the average run out and compare it with the specified tolerance.

Real-world applications of run out measurement include the automotive industry, where it is used to ensure the proper alignment of engine components, and the manufacturing industry, where it is used to identify and correct defects in rotating parts.

Measurement of Concentricity

Concentricity refers to the condition where two or more geometric shapes share the same center point or axis. It is a measure of how well the center points or axes of different shapes align with each other.

While concentricity is related to run out, it is different in that it focuses on the alignment of center points or axes rather than the deviation from a reference point or plane.

To measure concentricity, techniques such as the dial indicator method and coordinate measuring machine (CMM) can be used.

The dial indicator method for concentricity measurement is similar to that for run out measurement. The indicator is placed in contact with the surfaces of the objects being measured, and the readings are taken at multiple points.

A CMM, on the other hand, is a more advanced and automated measurement system. It uses a probe to measure the coordinates of multiple points on the objects and calculates the concentricity based on these measurements.

Let's walk through a typical concentricity measurement problem and its solution:

1. Set up the dial indicator or CMM equipment.
2. Position the indicator or CMM probe on the surfaces of the objects.
3. Take readings at multiple points and calculate the average concentricity.
4. Compare the calculated concentricity with the specified tolerance.

Real-world applications of concentricity measurement include the aerospace industry, where it is used to ensure the proper alignment of turbine blades, and the medical industry, where it is used to measure the concentricity of medical implants.

Advantages and Disadvantages of Measurement of Run Out and Concentricity

Advantages

1. Ensures proper alignment and balance of rotating parts: Run out and concentricity measurements help ensure that rotating parts are aligned correctly, reducing vibrations and improving the overall performance and reliability of mechanical systems.

2. Helps in identifying and correcting manufacturing defects: By measuring run out and concentricity, manufacturers can identify and correct defects in the production process, leading to higher quality products.

Disadvantages

1. Requires specialized equipment and expertise: Run out and concentricity measurements often require specialized equipment, such as dial indicators and coordinate measuring machines, as well as expertise in using these instruments.

2. Can be time-consuming and costly: Performing run out and concentricity measurements can be time-consuming, especially when multiple measurements are required. Additionally, the cost of the equipment and training can be significant.

Conclusion

In conclusion, the measurement of run out and concentricity is essential in metrology and mechanical measurements. These measurements ensure the proper alignment and balance of rotating parts, help identify and correct manufacturing defects, and improve the overall performance and reliability of mechanical systems.

By understanding the fundamentals of run out and concentricity measurements, different measurement techniques, and their real-world applications, engineers and technicians can make informed decisions and ensure the quality and precision of their work.

Summary

The measurement of run out and concentricity is essential in metrology and mechanical measurements. Run out refers to the deviation of an object's rotating axis from its true geometric center, while concentricity refers to the alignment of center points or axes. Run out can be measured using techniques such as the dial indicator method and laser measurement method, while concentricity can be measured using the dial indicator method and coordinate measuring machine (CMM). These measurements have advantages in ensuring proper alignment and balance of rotating parts and identifying manufacturing defects, but they also have disadvantages in terms of requiring specialized equipment and expertise and being time-consuming and costly.

Analogy

Imagine you are a chef preparing a cake. The run out measurement would be like ensuring that the cake is perfectly centered on the rotating cake stand, while the concentricity measurement would be like making sure that the layers of the cake are perfectly aligned with each other. Both measurements are crucial to ensure a beautifully balanced and aligned cake.